Various types of electric power tools are commonly used in construction, home improvement, outdoor, and do-it-yourself projects. Conventional power tools generally fall into two categories—corded power tools that are powered by an AC power source, e.g., an AC mains line, and cordless power tools that are powered by one or more DC power sources, e.g., a rechargeable battery pack.
Corded power tools generally are used for heavy duty applications that require high power and/or long runtimes, such as heavy duty sawing, heavy duty drilling and hammering, and heavy duty metal working. However, as their name implies, corded power tools require the use of a cord that can be connected to an AC power source. In many applications, such as on construction sites, it is not convenient or practical to find a continuously available AC power source and/or AC power must be generated by a portable power supply such as a generator, e.g. gas powered generator.
Cordless power tools generally are used for lighter duty applications that require low or medium power and/or short runtimes, such as light duty sawing, light duty drilling, and fastening. As cordless tools tend to be more limited in their power and/or runtime, they have not generally been accepted by the industry for all applications. They are also limited by weight since the higher capacity batteries tend to have greater weight, creating an ergonomic disadvantage.
Generally, conventional power tool battery packs may not be able to run conventional corded power tools or other corded electrical devices, while untransformed AC power may not be able to be used to run cordless power tools. Further, the battery packs for cordless power tools may require frequent recharging, may be expensive to purchase, and may be cumbersome to manage on a large construction site.
There are portable power supplies (sometimes referred to as inverters) that utilize batteries to provide power to an inverter which in turn provides AC output power to operate corded power tools designed to operate from wall/AC mains line power. These conventional battery based portable power supplies utilize integral batteries or conventional sealed lead acid (SLA) batteries. Although this allows the user to operate the corded power tool without having access to wall/AC mains line power, it does not allow the user to remove the battery from the portable power supply and use the battery to operate a set of cordless power tools. In other words, conventional systems provide for a battery pack for operating a set of cordless power tools and a battery for operating the battery based portable power supply wherein the battery pack for operating the set of cordless power tools cannot supply power to the portable power supply and the battery for operating the portable power supply cannot supply power to the cordless power tools. In the power tool industry, it is desirable to be able to use cordless power tool battery packs to drive the corded power tools. In addition, it is desirable to use cordless power tool battery packs to run non-power tool electrical device that are also designed to operate from wall (AC, mains line) power.
Another aspect of this disclosure is operating electrical devices that normally operate on mains line power, for example corded power tools, to simultaneously use the mains line power and battery power to increase the power available to perform work.
Traditionally the mains line power supply in the US is limited to 15 or 20 amps from a 120 volt AC power receptacle. Because the 15 amp branch circuit is relatively common conventional devices that plug into a standard 120 volt AC power receptacle are designed around this 15 amp limit. Such a design limits the input power from the AC mains line to about 1800 watts and thus the output power of a typical motor will be about 1200 watts, taking into account various system efficiencies. For short durations these power levels may be exceeded, but at the risk of opening the circuit protection device associated with the branch circuit supplying the load. There are many power tool applications that would benefit from the power beyond what can be effectively delivered through the 120 volt AC power receptacle. Currently the only options for these applications are to utilize a special receptacle, a generator with special receptacles or alternative motive power such as an internal combustion engine. This aspect presents a method and system to deliver higher operating power without special receptacles or internal combustion engines attached to the electrical device.